secrets-of-mental-math-malestrom

Products of a Misspent Youth: Basic Multiplication 41
224 (200 20 4)
9
200 9 1800
20 9
1
8
0
1980
4 9
3
6
2016
When you are first tackling these problems, repeat the
answers to each part out loud as you compute the rest. In the
first problem, for example, start by saying, “Twenty-eight hundred
plus five hundred sixty” a couple of times out loud to
reinforce the two numbers in memory while you add them
together. Repeat the answer—“thirty-three hundred sixty”—
several times while you multiply 9 7 63. Then repeat
“thirty-three hundred sixty plus sixty-three” aloud until you
compute the final answer of 3423. If you are thinking fast
enough to recognize that adding 60 63 will require you to
carry a 1, you can begin to give the final answer a split second
before you know it—“thirty-four hundred and . . . twentythree!”
Let’s end this section on 3-by-1 multiplication problems with
some special problems you can do in a flash because they
require one addition step instead of two:
511 (500 11)
7
500 7 3500
11 7
7
7
3577